Electronic devices such as servers, desktop computers, and laptop computers can often be alternatively powered by different power sources depending on the mode of operation. For example, a standby mode may use a standby power source that provides only a minimum amount of power necessary to keep the electronic device in standby mode. However, a main mode may require a larger amount of power than the standby mode. Thus, a separate main power source may be required to provide the power needed for operation in the main mode. Power source switching circuits can be used to switch between standby power sources and main power sources.
To prevent a large inrush of current during startup, main power source switching circuits also utilize soft-start functionality, where the power provided to the electronic device is slowly increased from zero to the full amount of the standby power sources. The gradual increase to the standby power prevents components of the electronic device from being damaged. However, the presence of soft-start functionality can often cause the power provided to the electronic device to temporarily decrease when switching back to standby power.
Thus, there is a need for a power source switching circuit that can effectively switch between standby power and main power; provide soft-start functionality when initially switching to standby power; and prevent temporary power or voltage decreases from occurring when switching back to standby power from main power.